The Role of Robotics in Total Knee Replacement Surgery

Introduction

Robots were still just something of sci-fi lore in the mid 2000s. Most of us specializing in knee replacement surgery couldn’t imagine a world in which a robot was used in knee replacement surgery. Me included…until I was introduced to an orthopaedic robot in 2006 by an Orthopaedic surgeon friend who had been working with a small start-up on exactly that. After a few hours in the lab playing with a relatively crude version of this incredible technology, I was hooked. I saw the promise of the robotic device, in its ability to improve the accuracy of the orientation of bone cuts and soft tissue balance that are so important in knee replacement surgery. Back in Philadelphia, it took a year to convince my hospital to make the $1.2 million dollar investment in the robotic system. But they did, and that started my nearly two decades of clinical and academic involvement with robotics for knee replacement surgery.

In the early years of robotics, our goal was first and foremost to simplify the procedure and make it easier for surgeons to consistently prepare the bone and align the components with optimal accuracy and balance the soft tissues (ligaments, etc.) around the knee. And we hoped, of course that this would subsequently lead to improved functional results and increased implant durability, not just in the hands of highly specialized surgeons, but more importantly perhaps, in the hands of less specialized and less experienced surgeons who might not be getting the same results as the “experts.”

Initially, as we worked to advance the field, there was a good deal of skepticism amongst many of our surgical colleagues who thought that the expense, learning curve, and lack of proof rendered the class of technology unnecessary, and adoption of robotics for knee replacement was limited to a relatively small handful of us. It wasn’t until around 2014 that we started to see a significant uptick in enthusiasm towards, and usage of, robotics. Now robots are considered mainstream and used commonly in hospitals and ambulatory surgery centers during knee replacement surgery. To some extent this paradigm shift has been driven by the demographic change amongst orthopaedic surgeons. As the percentage of digitally inclined joint replacement surgeons under the age of 50 reached a threshold, the numbers of surgeons using robots also started growing. The status quo was no longer acceptable. Now, as of 2025, almost two-thirds of the members of one of our largest national hip and knee joint replacement academic societies are using robotic assistance during their knee replacements. Back in 2016, financial analysts suggested that once robotic penetration in the joint replacement market achieved a 35% level, orthopaedic surgeons, hospitalsand patients would routinely demand access to robotic technologies – that threshold is here and yes people are asking about robots at their appointments. We recently published a study that found that 40% of our patients want their knees replaced with the assistance of a robot.

Outcomes of Robotic Knee Replacement

The data has emerged and, for the most part, the outcomes are reflective of our expectations. First, time and again, studies have shown improved component position and alignment when knees are replaced with robotic assistance. Second, when we compare the outcomes of knee replacements done by specialist joint replacement surgeons, using either conventional instrumentation or robotic assistance, patients whose knees are replaced with robotic assistance are a little bit further along in their recovery at 6 weeks and up to 3 months (and sometimes longer), but by a year after surgery and beyond, the conventionally done knee replacement patients catch up. So, what this should tell you (the patient) is if you happen to see an expert specialized knee replacement surgeon who does not use a robot, don’t stress. Our published data, and others’, show that in the hands of specialized surgeons, by a year and beyond, your outcomes should be equivalent, whether a robot was used or not. We just can’t say the same about lower volume, non-specialist surgeons doing knee replacements.

In fact, data from international registries that track the outcomes of all patients receiving knee replacements in their particular countries, show that in the hands of surgeons with all different levels of experience and expertise, the failures related to errors of alignment and balance are significantly reduced when a robot is used. In other words, the robot can neutralize the problem of surgeon inexperience when it comes to knee replacements. On the other hand, expert surgeons are expert surgeons, with or without robotic assistance.

Patients have a healthy concern about the safety of using a robot. The robots we use today are called semi-autonomous (they are tools that are used in collaboration with the surgeon; they do not function independently). Studies have found no significant increase in the incidence of soft tissue or bone injuries related to use of the currently available robotic bone preparation technologies.

Potential Future Innovations in Robotics

As analytics platforms continue to evolve, it is our hope that within a few years we will better understand how decisions that we make during surgery - such as how we align the components for each patient, how much of the bone surfaces we remove (and its impact on how we choose the implant sizes), and how tight or loose we make the soft tissues around the knee – ultimately impact clinical outcomes. With the information thus derived, it is our hope that artificial intelligence algorithms will eventually be refined to guide surgical decisions in a highly efficient way and ultimately influence joint kinematics and outcomes specific for each individual patient.

Conclusion

Robotic assistance is enhancing the alignment and soft tissue balance in knee replacement surgery. Even in the hands of highly specialized surgeons, this seems to be accelerating the early recovery in the first few months after surgery. This is important, since more than half of our knee replacement patients today are still working or otherwise quite active. Amongst lower volume and less specialized surgeons doing knee replacement surgery, data emerging from international registries is showing a reduction in failures from errors in component alignment or imbalance when using a robot. In other words, robotic assistance makes less experienced surgeons better. We are certainly not done innovating in the robotics space. The paradigm of knee replacement surgery will continue to evolve to further improve the field and optimize patient outcomes. To schedule a consultation on knee replacement surgery, visit our appointments page today.

REFERENCES

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